Elsevier

Ecological Economics

Volume 72, 15 December 2011, Pages 88-96
Ecological Economics

Analysis
Trophically balanced sustainable agriculture

https://doi.org/10.1016/j.ecolecon.2011.08.017Get rights and content

Abstract

Considering an economy without fossil fuels, literally built from the ground, then up, we developed several interactive research models of biointensive farms that use no fossil fuels. Quantifying and summarizing total human labor–energy input and total caloric energy output, we demonstrate that a successfully designed farm can produce a positive energy-return-on-investment (EROI) leaving excess caloric energy available for building economic-community structures (e.g., schools and hospitals). Farm products with negative EROI must be coupled with other products with positive EROI to assure nutritionally balanced diets are maintained while still achieving an overall positive EROI for the total agroecological operation. We show that similar to the ecosystem, energy budgets are tight which makes for difficult decisions on diet, farm plot diversity, and energy profitability for future growth. Considering the totality of this low energy agro-system based economy, we simplify many operational variables into a unique graphical solution space, which reveals both reasonable expectations of agroecological EROI performance, and extreme asymptotes, beyond which indicate regions of system failure.

Highlights

► We theoretically demonstrate a successfully designed farm can produce a positive energy-return-on-energy-investment (EROI). ► Similar to the ecosystem, we show that actual energy budgets of sustainable agroecological farming operations are tight. ► We show that growing a nutritionally balanced diet is possible within a positive EROI sustainable farm operation. ► We reveal extreme asymptotes of sustainable farming EROI performance beyond which indicate regions of system failure.

Introduction

The inevitable peak production in fossil fuels (Hirsch et al., 2005, Kharecha and Hansen, 2008) coupled with an increasing world population demand (EIA, 2007, USCB, 2008) will result in dramatic changes with regard to anthropocentric energy systems and their respective local and distal supporting ecosystems. Also, reasonable CO2 emission scenarios (e.g., global temperature rise held to less than 2 °C) will require extreme reductions in fossil fuel usage in the near decades [e.g., 40% reduction from 1990 levels in the next 10 years (Allison et al., 2009) and 80% reduction from 1990 levels in the next 40 years by developed countries (Meinshausen, 2007, Watkins, 2007/2008)]. Newell et al. (2006) summarize the potential and range of effects of various policies introduced to reduce energy consumption and carbon emissions. Yet, accounting for existing and projected new developments in energy efficiency within modern society, the National Academy of Engineering (Lave, 2009) reports that if the U.S. continues with expected technological improvements, it can only reduce approximately 30% of the energy that would have been used by 2030. Maréchal (2010) shows that energy consumption habits contradict rational choice theory “where the current carbon-based Socio-Technical System constrains and shapes consumers' choices through structural forces”. Referencing social psychology, Townsend and Bever (2001) succinctly summarize, “most of the time what we do is what we do most of the time” after showing that the pursuit of social and economic stability is what characterizes modern energy consumption trends and associated research.

Countering the ongoing research paradigm of improving current devices, processes, and social efficiencies (e.g., Franzluebbers and Francis, 1995, Hülsbergen et al., 2001, Mrini et al., 2002) to ease the transition from fossil fuels, we specifically consider an agro-economy with no fossil fuels. This perspective forces the associated anthropocentric sub-sector to research, engineer, and operate within a local eco-trophic envelope. More importantly, through this approach, novel insight, perspectives, and ideas not apparent in Maréchal's existing Socio-Technical System and its modern energy models are developed. Moreover, this approach may generate technologies capable of affecting Less Developed Countries (LDCs) in a meaningful way. University of Georgia's (UGAs) Low Energy Systems (LES) modeling program is conducting research to assess the needs of modern population levels with little to no fossil fuels. Here, we present models of non-fossil-fuel vertically integrated agricultural systems where energy (Caloric) outputs are managed to exceed human labor-energy inputs. (We use the standard convention where one food Calorie equals 1000 chemist calories (1 kcal) where the former is usually capitalized and the latter is not.) Ostensibly, excess labor energy or biofuel crops are then available to be redirected from the local agricultural operation to community and economic development. Thus, a local economy can be launched.

As high-density energy supplies dwindle or the negative ramifications of fossil fuel consumption become better understood, plans and corresponding efforts to reduce energy consumption are a looming priority in a variety of sectors of the US economy. Representing a large energy consumer in the U.S., the nation's food supply system is at the center of this issue. The current American food supply is driven almost entirely by non-renewable energy sources [consider the often cited trend that U.S. agricultural labor, as a percentage of the economy's total labor, went from 64% in 1850 to 2% by the year 2000 (Smil, 2008)], which permits our modern food production and distribution system, including sustainable agriculture, to use significantly more energy than it produces. Pimentel and Pimentel (1983) established an energy input–output perspective as a measure of agricultural efficiency showing, for example, that fruits and vegetables required two Calories to produce one food Calorie of output and various animal products required 20, even up to 80 Calories of input energy for each food Calorie of output. Although many studies have followed, Gussow (1991) is frequently cited as showing 15 Calories of energy input were used for each Calorie of energy produced in the American food supply system in the 80s. The estimates continue to vary due to varying boundaries, quality of data sets, volume of products produced, etc. To provide a visual perspective to this relationship, Fig. 1 shows Heller and Keoleian (2000) data (because it is reasonably recent) which approximate seven equivalent Calories of energy consumed by the U.S. food system for each agricultural Calorie yielded. These embodied energy inputs continue to be evaluated and debated. For example, packaging has wide variability and is often estimated as requiring much higher energy inputs (Pimentel et al., 2008, Pimentel and Pimentel, 2008) which is one research area that may explain Heller and Keoleian's lower ratio than past estimates of the energy returned on energy invested (EROI) for the U.S. food system. Despite variations in estimates, the summary conclusion as depicted in Fig. 1 is that the EROI in agriculture is not considered sustainable when compared to self-organizing ecosystems.

Although a wide range of public and private resources are developing to both understand and reduce nonrenewable energy consumption (examples include: DOE's Energy Efficiency and Renewable Energy Program and their Alternative Fuels Program, the Bioenergy Feedstock Information Network (BFIN), and the university-based Sun Grant Initiative, etc.), the initiation of energy studies specifically for agriculture has been considerably smaller, and noticeably more limited with regard to sustainable agriculture. Biofuels are one exception and an area of intense research (DOE (U.S. Department of Energy), 2003, EUROPA, 2007, Tilman et al., 2009); however, agriculture intensive energy research is primarily dominated by renewable energy research that is secondarily applied to agricultural systems. For example, the USDA's Sustainable Agriculture Research and Education (SARE) organization's 2006 workshop was organized to “bring together various groups and agencies that focus on renewable energy and sustainable agriculture to exchange information and identify areas of commonality”. Yet, the concluding summary of potential topics for research almost exclusively referenced plant-based fuel areas (a.k.a., biofuels) to aid farm operations or simply for farm production and sale. The summary did identify, however, that an increase in energy conservation needs to be added to future discussions. A comprehensive systems approach with a long-term sustained effort towards the understanding of energy in agriculture is needed where organic farming currently recognizes the use of mechanical cultivation and in general embraces energy conservation only indirectly by promoting the reduction of climate change practices (for example, The Rodale Institute). No policies, goals, or plans are in place to address renewable or nonrenewable energy in sustainable agriculture. As such, we jump ahead of the current issue and consider organic operations without fossil fuels to begin engineering the foundation for future considerations and to identify technology and insight that can potentially be inserted into today's modern or less developed societies.

First, we discuss the sustainable farming method used in the modeling effort (GROW BIOINTENSIVE®) primarily because it has a dataset of product yields available in the literature and, due to its mature stage of development, it minimizes the variability of several input values for our theoretical model. We address how vitamin B12, of particular concern in plant-based diets, is accommodated for this sustainable farm model simulation. We then articulate the software and computational aspects of the model inputs, outputs, and how these are coupled. Several scenario farms representing different inputs and outputs are generated, presented, and discussed. We conclude with a discussion of the ramifications of an energetically balanced sustainable agriculture system.

Section snippets

Materials and Methods

For development and corresponding assumptions, the theoretical model is assumed to be a biodynamic French intensive style farm located in the Piedmont Ecoregion of Georgia, USA. The Georgia Piedmont is a geographically contiguous area in the upper half of the state situated between the Coastal Plain of central to south Georgia and the Blue Ridge Ecoregion to the north. The Piedmont is characterized by mineral and rock deposits and readily apparent red iron oxide laden soils. Biodynamic French

Results

Considering the infinite range of farm system solutions as they pertain to varying inputs and subsequent outputs, we specifically explore limiting factors to improve our understanding of sustainable agriculture's capacity and limitations, particularly as to how system responses affect the farm's combined energy output. The objective is to identify and quantify respective boundary limits with respect to, for example, harvest diversity, total energy output, and farm efficiency. Farm efficiency is

Discussion

As natural resources continue to be depleted locally, sustainable agricultural systems will eventually move towards material- and energy-neutral balances with regard to their adjacent ecosystems (e.g., carbon, nitrogen, water, biota, energy, etc.). The luxury of distal supplies or deposits to accommodate unbalanced local environmental relationships is diminishing. System approaches such as low-input agriculture (House and Brust, 1989, Pimentel et al., 1989) or traditional ecological knowledge

Conclusion

Considered in total, local ecosystems generally acquire no energetic benefit from fossil fuels. This model essentially develops an anthropocentric economy similar to the ecosystem that trades in temporally relevant nutrients and energy flows. Quantifying and summarizing the total farm Caloric output for a single farmer input, we demonstrate that a successfully designed farm can produce a positive energy-return-on-investment (EROI) leaving additional Caloric energy to be routed towards

Acknowledgements

We would like to personally thank John Jeavons and Ecology Action for a lifetime of work and dedication to generate the information and dataset integral to this research. We would also like to thank two Anonymous Reviewers for their thoughtful insight that significantly improved this manuscript. Finally, we would like to thank UGA's Faculty of Engineering and the Systems and Engineering Ecology Program for their ongoing support of our research.

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